Data Package Server does not support encrypted private keys

[tkuester]

Currently, while the ssl.key_pw field lets the COT server use encrypted SSL private keys, the data package server does not. According to benoitc/gunicorn#2410, Gunicorn will be switching to using Python's SSLContext object, which will allow for this in the future. A pull request is in, but not yet merged. Once it's in, we will add this in!